Curing and sealing compounds are commonly used in the concrete industry to enhance physical property development of freshly poured concrete mixes. Desired materials are those that combine ease of application, effective film forming characteristics, the ability to penetrate and seal pores or imperfections in the concrete, low hazards characteristics, minimal or no VOC emissions, and availability at a competitive cost. However, many of the materials currently offered today do not provide the favorable mix of such attributes required by the concrete industry.
Concrete curing compounds are typically applied as a coating to the surface of freshly poured concrete, in order to provide a water impermeable layer to keep moisture in the concrete mix from evaporating too quickly, thereby maintaining a proper hydration level for correct curing and compressive strength development. Concrete sealing compounds are used in the long term to protect the concrete mixture from materials like, alkali metal salts, which can leach in and lead to cracking, early degradation or failure.
Currently available materials for curing or sealing purposes include acrylic based resins, emulsion polymers, wax emulsions, urethane based polymers, naturally derived materials and others. Some are used for individual purposes, either sealing or curing, and others serve dual purposes as both sealing and curing compounds. These materials are typically formulated with pigments such as titanium dioxide (TiO2) to serve as a reflecting surface to sunlight, to minimize heat absorption thereby lowering the temperature of the curing concrete to allow for proper curing, strength development and reducing internal stresses.
Water based materials for both sealing and curing applications are highly desirable because of ease of handling and clean-up, the elimination of volatile organic compounds, and the elimination of flammability hazards associated with solvents. While solvent based materials have demonstrated the ability to meet standard performance requirements for curing, they are used preferentially in sealing applications.
The prior art provides for wax emulsion compositions, and a process for improving the early strength of cement aggregate products, in a stabilized aqueous emulsion with a surfactant such as alkali metal salts of fatty acids, alkali metal salts of sulfated fatty acids, alkali metal alkyl sulfates, alkali metal alkyl sulfonates, alkali metal aryl sulfonates, alkali metal alkyl lauryl sulfonate, alkali metal salts of alkylated naphthalene, alkali metal salts of lignosulfonic acid, condensation products of ethylene oxide and polyalkylene glycols, fatty acid glycerides, fatty acid amides, polyethylene sorbitol esters of fatty acids, quarternary ammonium halides, sorbitan esters, sulfonated or sulfated fatty acid esters or amides, and sulfonic acid.
The prior art also indicates that the introduction of wax emulsion compositions is specifically targeted to curing applications of concrete products not to dual purpose curing and sealing functions. Wax emulsions have been identified as good film-forming materials, but lacking the overall water retention capability unless coupled with other resins or components, such as hydrocarbon resins for example.